Device for winding off flexible material



Sept. 2, 1969 R T ETAL 3,464,644

DEVICE FOR WINDING OFF FLEXIBLE MATERIAL Filed May 12, 1967 INVENTORS(J's/m KARA m AT'A j TEVAN C. L EBONOI/IC ATTORNEY United States Patent3,464,644 DEVICE FOR WINDING OFF FLEXIBLE MATERIAL Jean Karamata andStevan Celebonovic, Geneva, Switzerland, assignors to Rolpa S.a.r.l.,Carouge-Geneva, Switzerland, a corporation of Switzerland Filed May 12,1967, Ser. No. 638,092 Int. Cl. B65h 25/22 US. Cl. 24275.43 8 ClaimsABSTRACT OF THE DISCLOSURE A device for unwinding flexible materialrolled on a rotary support, said material acting on a movable memberoperatively connected to a brake acting on the support, wherein an armis located at such a point that it is subjected to a force varying inrelation with the radius of the winding of the material on said support,said variable force controlling the braking action of said brake.

Background of the invention In the different technical fields, it isoften desirable to wind off some flexible material rolled on a rotarysupport so that the tension to which the material is subjected remainsconstant. It is necessary that the tension of the material is notinfluenced by the variations of the speed of the unrolling, or by thevariation of the diameter of the rolling up on the rotary support, thediameter is continually diminishing with the winding 011 of thematerial.

The simple devices which permit an unrolling at a reasonably constanttension, include an arm which acts on the brake of the rotary support,the wound off material running over a cylinder or over a wheel held bythe free end of said arm so that said arm is displaced more or lessaccording to the tension of the body. The brake is maintained tight by aspring or something similar, and the tension of he wound off materialacts so that the brake is loosened with an alternative action of thespring. As soon as the tension of the material falls under a determinedvalue, the brake tightens while, when the tension becomes too great, thebrake is loosened. Such devices are, for example, being used on rollingmachinesto make electric windings.

In such devices, a variation of braking of the rotary support iscontrolled by the variation of the tension of the body in such a waythat a constant tension of the body which is being unwound cannot beobtained.

In order to obtin a constant tension, much more complicated devices havebeen developed, including electronic devices which yield excellentresults but which are also very costly.

The present invention is directed to a very simple device which permitsobtaining an extremely constant tension of the material which is beingwound off from the rotary support.

Summary of the invention This invention relates to a device for windingoff a length of flexible material rolled on a rotary support. When thematerial leaves the support, it acts on an arm, the displacements ofwhich influence a brake retaining the material on the rotary support inorder to make the tension of the material reasonably constant. Suchdevice is characterized by the fact that the arm is placed so as to besubjected to a force which depends on the radius of the material rolledon the rotary support, which force is conveyed to the brake.

3,464,644 Patented Sept. 2, 1969 Brief description of the drawingDescription of the preferred embodiment With reference to FIG. 1, thedevice includes a frame comprising two metal plates 1 and 2 which areparallel and connected with each other by cross-bars 3. The materialwhich is to be wound ofl is a roll of paper 4 carried by an axle 5 whichis rotatable within two bushings 6 and 7 respectively, which are securedto the metal plates 1 and 2.

The paper is wound off from roll 4 in the form of a strip 8 passing overa roller 9. The strip of paper is pulled by a take-up device, not shown,for feeding a machine which can be used for example, to make rollsformed by several strips placed one over the other, or a machinedispensing paper in sheets.

The roller 9 is fixed in such a way as to rotate on an axle member 10journaled in bearings 11 and 11 attached to the metal plates 1 and 2.The axle member 10 includes an arm 13, the position of which depends onthe position of the roller 9. The arm 13 is connected by a rod 12 atright angles thereto to an arm 14 the movement of which is controlled bya piston 29 of a hydraulic system 15 for regulating the braking free ofa "brake 16.

The brake 16 is a well known type of disk brake in which a disk 17 fixedon the end of the axle 5, runs through a slot in a block 18 whichincludes two shoes, not shown in FIG. 1, which are subject to the actionof hydraulic fluid in the system 15 in order to exert the desiredbraking force on the disk 17.

The block 18 is slidably on the shaft 19 and its position can beadjusted in a manner parallel to the axis of the roll 4 by means of ascrew 20 which has a knob 21 rigid therewith. Thus, by adjusting theposition of the brake 16, the axial position of the roll 4 can beadjusted with great accuracy.

FIG. 2 shows diagrammatically the circuit of the hydraulic circuit whichcontrols the brake 16. The circuit includes a first cylinder 22 whichcommunicates through a pipe 23 with a second cylinder 24. The cylinder22 is closed by a piston 25 which exercises a constant pressure on theliquid which fills the cylinders 22 and 24 and the pipe 23 under theeffect of the weight 26 connected to the end of a lever 27 which acts onthe piston 25. The pressure existing in the cylinder 24 is conveyed intoa third cylinder 28 by means of a double acting piston 29. The liquidwhich is subject to the pressure of the piston 20 exerts a force on ashoe 30 which slides in a cylinder in the block 18. Said last-mentionedcylinder is connected with the cylinder 28 by a pipe 31 whichcommunicates further with a cylinder 32 which is closed by a piston 33,which piston can be displaced by means of a screw 34.

The double acting piston 29 is connected with the end of the arm 14which is secured by means of rod 12 to the arm 13 of axle 10 whichcarries the roller 9. The axis of the roller 9 is disposed on a lineparallel to the axis of rod 12 connected to arm 13 and parallel to theaxis of the roll 4.

The above described arrangement permits obtaining a constant tension ofthe strip of paper 8 when it is wound off the roll 4 as can be seen fromthe following considerations:

The forces which act on the piston 29 are the followmg:

(l) The force F, due to the pressure exercised by the piston 25, pushesthe piston 29 towards the right, as

I X (cos ai) C G,

where r=rs, s being the radius of the roll 9.

Thus the resultant force Y acting on piston 29 is as follows:

The couple of braking M is proportional to Y and to the distance d whichmarks the radial distance between the axle S and the brake 16. Thatcouple is as follows:

Where K is a constant depending on the type of brake utilized, on thedimensions of the pistons, of the coefficient of friction of the brakeetc. The couple of braking is equal to the couple exercised on the axleby the tension X of the strip on the roll 4 of the the radius r whichgives the following relation:

1" 1) X1 -KYd-Kd[FX(cos 01- By transforming the Equation 3 in order toobtain X, it results:

b s 1 Kb In the Equation 4, the only variable is r, so that it ispossible to obtain that the tension X remains constant by cancelling thefactor of r, i.e.:

1 fi d ac It is therefore necessary to construct the device as to a d TE 6 When the condition 6 is fulfilled, the Equation 4 becomes:

cos n+ (7) oralso:

a F 'ggi i As can be seen it is sufiicient to fix the initial force F,due to the pressure of the piston 25 in order to determine the tension Xwhich one wishes to obtain on the strip 8 which is being wound ofi fromthe roll 4. Otherwise, the variation of the radius of the roll 4automatically controls the modifications which have to be made in thebraking in order to maintain constant the tension X of the strip. Onaccount-of the very weak elasticity of the hydraulic control, the forcesacting on the roller 9 are conveyed to the double acting piston 29without the roller 9 being displaced appreciably. When the wear whichshows up after a certain time on the brake 16 causes too great adisplacement of the roller 9 in relation to its ideal posi- 4 tion, itis easy to return the roll into the desired position by tightening thescrew 34.

The described construction can of course be easily modified so that thedisplacements of the roller 9 have practically no influence on thetension X of the tape. In fact, it is suificient, on one hand, to placethe revolving point-of the arms'13, 14 on the axis of the axle 5 and, onthe other hand, to place the cylinder 35 so that the angle a is nil. Inthat way, the angle which the tape 8 coming out of roll 4 forms with thearms will be constant because the point of connection of the armscorresponds with the axis of the roll 4. Furthermore, displacements ofsubstantial magnitude of roller 9 cause only a very small variation ofthe angle a. The pressure exerted on the arms fixed in this manner willbe, to a great extent, independent of the position of said arms.

It is understood that the principle of the device described can beapplied to different technical fields. Its use seems particularlyindicated in the case of winding mechanisms for electric Wires or fortextile fibres as well as for braking paper rolls in printing presses.

The device described can be modified and, particularly, the doublepiston can be replaced by two elastic tubes connected to the arm 14. Byan appropriate choice of the dimensions of the whole arrangement and thedistances a, b and c, it is possible to obtain a simple correspondencebetween the pressure in the cylinder 22 and the force of traction to beexercised on the strip 8. For example, it is possible to obtain a forceof traction of 1 kg. on the strip 8 for a pressure of 1 kg./cm.

As another solution, the same result can be obtained by using a brakingdevice including two brakes, one of which can be regulated so as tofurnish a constant braking force, while the other will be connected withroll 9 so as to furnish a braking force which will be proportional tothe result of the forces which act on roll 9.

The constant pressure exerted on the face of piston 29 by the liquidwhich is subject to the weight 26 can also be obtained mechanically by aspring which acts directly on the piston 29. It should be noted that insuch case, like in the one represented in the drawing, the force due tothe tension of the strip is opposed to the constant force, which is veryadvantageous in order to obtain a good compensation of the dynamiceffects. In fact, when the traction exerted on the tape 8 ceasessuddenly, the tension of the tape becomes nil, and all the constantforce acting on the piston 29 becomes available in order to assure thebraking of roll 4. In that way, that roll is blocked almost immediately.

It is understood that the described principle of regulating can also berealised with the same efficiency by providing a mechanical connectionbetween the roller 9 and the brake. The brake can be of any type, suchas a brakeshoe directly acting on axle 5. At any rate, itseems-preferable, in the latter case, that the shoe includes a portionwhich enters into at least one ridge in form of a-V pro- 7 vided on theaxle 5, so that, by displacing the shoe sidewards, the axial position ofthe axle 5 can be fixed at the same time.

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In any case, it is of advantage to build in a shock absorber, preferablya hydraulic one, in order to resist the rapid displacements which couldarise on roller 9 by the sudden variations of the tension of the strip.Such varia tions happen, in fact, when the roller has a slight defect inits centralizing, and it is preferable to avoid a condition where thevariations exert a reaction on the braking force.

We claim:

. 1. In a device for maintaining constant tension on a rotary supportfrom which a roll of strip material is being unwound, a hinged arm onwhich the material leaving the support exerts a force proportional tothe tension of the material and the function of the relative diameter ofthe roll of material on the rotary support, a brake acting on saidrotary support, said arm being subjected to a return force and acting onsaid brake, said device characterized by the fact that said return forceis selected so as to balance the action of the constant component of theforces exerted by the material on said arm for a given unwindingtension, the length of said arm and the location of its hinge axis beingselected as a function of the braking coefiicient, so that the componentof the forces, which is variable depending on the diameter of thewinding, produces a braking torque equal to the product of the tensionon the elongated body and the radius of the roll of material.

2. A device as claimed in claim 1, including a roller connected withsaid arm, said material being in contact with said roller, said rollerlocated substantially in a plane defined by the axis of the roll ofstrip material and the hinge axis of said arm.

3. A device as claimed in claim 2, wherein the distance between therotary support and the point of action of the strip material on said armis determined in terms of the relation of transmittal of the forceexerted on the arm against the brake and is dependent on the constant ofthe brake.

4. A device as claimed in claim 3, wherein the brake is hydraulic andsaid arm acts on a piston controlling the hydraulic circuit of saidbrake, said piston being subjected to a substantially constant forceopposite to and higher than that applied by the arm.

5. A device as claimed in claim 4, including a second hydraulic circuitadapted to produce the substantially constant force acting on thecontrol piston.

6. A device as claimed in claim 4, wherein a weight applies saidsubstantially constant force to said control piston.

7. A device as claimed in claim 4, wherein said hydraulic circuit actingOn the brake comprises an adjustable piston for wear take-up of thebrake.

8. A device as claimed in claim 1, wherein said brake is a disc brakeand the shoes of said brake are carried by an adjustable block which ismovable in parallelism with the axis of the rotary support, said supportbeing rotatably and slidably mounted in bearing means so that the axialposition of the rotary support is set by the position of the brakeblock.

References Cited UNITED STATES PATENTS 1,859,577 5/1932 Armbrecht242--75.43 1,884,183 10/1932 Pearson 24275.43 2,965,326 12/1960Rockstrom 24275.43

NATHAN L. MINTZ, Primary Examiner

